Simple ICS Generation class for PHP

SimpleICS.php

<?php /*
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

Furkan Mustafa, 2015.04.06
- Updated 2015.04.09: Limit lines to 70 chars (spec is 75)
- Updated 2015.04.26: duplicate letter fixed by @PGallagher69 (Peter Gallagher)
- Updated 2015.04.26: Outtlook Invite fixed by @PGallagher69 (Peter Gallagher)
- Updated 2015.05.02: Line-limit bug fixed by @waddyvic (Victor Huang)

Adapted from: https://gist.github.com/jakebellacera/635416
Also see: https://www.ietf.org/rfc/rfc5545.txt

Development Sponsored by 77hz KK, Tokyo, http://77hz.jp

Usage:

$cal = new SimpleICS();
// $cal->productString = '-//77hz/iFLYER API//';
$cal->addEvent(function($e) {
	$e->startDate = new DateTime("2015-04-06T10:00:00+09:00");
	$e->endDate = new DateTime("2015-04-06T18:30:00+09:00");
	$e->uri = 'http://url.to/my/event';
	$e->location = 'Tokyo, Event Location';
	$e->description = 'ICS Entertainment';
	$e->summary = 'Lorem ipsum dolor ics amet, lorem ipsum dolor ics amet, lorem ipsum dolor ics amet, lorem ipsum dolor ics amet';
});

header('Content-Type: '.SimpleICS::MIME_TYPE);
if (isset($_GET['download'])) {
	header('Content-Disposition: attachment; filename=event.ics');
}
echo $cal->serialize();

*/

class SimpleICS {
	use SimpleICS_Util;

	const MIME_TYPE = 'text/calendar; charset=utf-8';
	
	var $events = [];
	var $productString = '-//hacksw/handcal//NONSGML v1.0//EN';

	static $Template = null;

	function addEvent($eventOrClosure) {
		if (is_object($eventOrClosure) && ($eventOrClosure instanceof Closure)) {
			$event = new SimpleICS_Event();
			$eventOrClosure($event);
		}
		$this->events[] = $event;
		return $event;
	}

	function serialize() {
		return $this->filter_linelimit($this->render(self::$Template, $this));
	}
}

class SimpleICS_Event {
	use SimpleICS_Util;

	var $uniqueId;
	var $startDate;
	var $endDate;
	var $dateStamp;
	var $location;
	var $description;
	var $uri;
	var $summary;

	static $Template;

	function __construct() {
		$this->uniqueId = uniqid();
	}

	function serialize() {
		return $this->render(self::$Template, $this);
	}
}

trait SimpleICS_Util {
	function filter_linelimit($input, $lineLimit = 70) {
		// go through each line and make them shorter.
		$output = '';
		$line = '';
		$pos = 0;
		while ($pos < strlen($input)) {
			// find the newline
			$newLinepos = strpos($input, "\n", $pos + 1);
			if (!$newLinepos)
				$newLinepos = strlen($input);
			$line = substr($input, $pos, $newLinepos - $pos);
			if (strlen($line) <= $lineLimit) {
				$output .= $line;
			} else {
				// First line cut-off limit is $lineLimit
				$output .= substr($line, 0, $lineLimit);
				$line = substr($line, $lineLimit);
				
				// Subsequent line cut-off limit is $lineLimit - 1 due to the leading white space
				$output .= "\n " . substr($line, 0, $lineLimit - 1);
				
				while (strlen($line) > $lineLimit - 1){
					$line = substr($line, $lineLimit - 1);
					$output .= "\n " . substr($line, 0, $lineLimit - 1);
				}
			}
			$pos = $newLinepos;
		}
		return $output;
	}
	function filter_calDate($input) {
		if (!is_a($input, 'DateTime'))
			$input = new DateTime($input);
		else
			$input = clone $input;
		$input->setTimezone(new DateTimeZone('UTC'));
		return $input->format('Ymd\THis\Z');
	}
	function filter_serialize($input) {
		if (is_object($input)) {
			return $input->serialize();
		}
		if (is_array($input)) {
			$output = '';
			array_walk($input, function($item) use (&$output) {
				$output .= $this->filter_serialize($item);
			});
			return trim($output, "\r\n");
		}
		return $input;
	}
	function filter_quote($input) {
		return quoted_printable_encode($input);
	}
	function filter_escape($input) {
		$input = preg_replace('/([\,;])/','\\\$1', $input);
		$input = str_replace("\n", "\\n", $input);
		$input = str_replace("\r", "\\r", $input);
		return $input;
	}
	function render($tpl, $scope) {
		while (preg_match("/\{\{([^\|\}]+)((?:\|([^\|\}]+))+)?\}\}/", $tpl, $m)) {
			$replace = $m[0];
			$varname = $m[1];
			$filters = isset($m[2]) ? explode('|', trim($m[2], '|')) : [];

			$value = $this->fetch_var($scope, $varname);
			$self = &$this;
			array_walk($filters, function(&$item) use (&$value, $self) {
				$item = trim($item, "\t\r\n ");
				if (!is_callable([ $self, 'filter_' . $item ]))
					throw new Exception('No such filter: ' . $item);

				$value = call_user_func_array([ $self, 'filter_' . $item ], [ $value ]);
			});

			$tpl = str_replace($m[0], $value, $tpl);
		}
		return $tpl;
	}
	function fetch_var($scope, $var) {
		if (strpos($var, '.')!==false) {
			$split = explode('.', $var);
			$var = array_shift($split);
			$rest = implode('.', $split);
			$val = $this->fetch_var($scope, $var);
			return $this->fetch_var($val, $rest);
		}

		if (is_object($scope)) {
			$getterMethod = 'get' . ucfirst($var);
			if (method_exists($scope, $getterMethod)) {
				return $scope->{$getterMethod}();
			}
			return $scope->{$var};
		}

		if (is_array($scope))
			return $scope[$var];

		throw new Exception('A strange scope');
	}
}

SimpleICS::$Template = <<<EOT
BEGIN:VCALENDAR
VERSION:2.0
PRODID:{{productString}}
METHOD:PUBLISH
CALSCALE:GREGORIAN
{{events|serialize}}
END:VCALENDAR

EOT;

SimpleICS_Event::$Template = <<<EOT
BEGIN:VEVENT
UID:{{uniqueId}}
DTSTART:{{startDate|calDate}}
DTSTAMP:{{dateStamp|calDate}}
DTEND:{{endDate|calDate}}
LOCATION:{{location|escape}}
DESCRIPTION:{{description|escape}}
URL;VALUE=URI:{{uri|escape}}
SUMMARY:{{summary|escape}}
END:VEVENT

EOT;

I would really like to use this code on my website. I'm quite new so I am hoping someone can be kind.

I use a database which only prints to pdf various fields from my database and inside that pdf are appointment details. I want to format the Pdf with a link which includes appointment details which will populate the simpleICS.php function via post method which will then download an ics file for the appointmentee can use.

I presume that the code below goes inside my functions.php and the simpleics.php placed in directory but how do you call that function from the actual page I am send the data to in a url string.

$cal = new SimpleICS();
// $cal->productString = '-//77hz/iFLYER API//';
$cal->addEvent(function($e) {
$e->startDate = new DateTime("2015-04-06T10:00:00+09:00");
$e->endDate = new DateTime("2015-04-06T18:30:00+09:00");
$e->uri = 'http://url.to/my/event';
$e->location = 'Tokyo, Event Location';
$e->description = 'ICS Entertainment';
$e->summary = 'Lorem ipsum dolor ics amet, lorem ipsum dolor ics amet, lorem ipsum dolor ics amet, lorem ipsum dolor ics amet';
});
header('Content-Type: '.SimpleICS::MIME_TYPE);
if (isset($_GET['download'])) {
header('Content-Disposition: attachment; filename=event.ics');
}
echo $cal->serialize();

Is there any way to include an attachment in the ICS file